1. Field of the Invention
The present invention relates in general to a tantalum nitride barrier for copper metallization in semiconductor components and the process for its fabrication. In particular, the present invention relates to a tantalum nitride barrier having superior diffusion blocking and electrical conducting characteristics that is fabricated in a procedure based on metal-organic chemical-vapor-deposition (MOCVD) for copper metallization in semiconductor components and its process of fabrication.
2. Technical Background
Aluminum used as the material for metallization in the fabrication of semiconductor devices has its inherent limitations. As the trend of miniaturization and functional improvement of semiconductor devices continues, metals having better electrical conducting characteristics than aluminum have to be used for metallization.
Refractory metal nitrides such as TiN and TaN have been proposed and studied to establish thermally stable and adhesive metallization schemes with low resistivity. For example, M. Witmer in an article in J. Vac. Sci. Technol. A. 3, 1797 (1985), and M. A. Farooq et at. in their article in J. Appl. Phys., 70, 1369 (1991), proposed depositing nitrides of Ti and/or Ta for such purposes. However, these metal nitride materials have been deposited via reactive sputtering of Ti and Ta targets in an Ar-N.sub.2 atmosphere where the step coverage degrades rapidly as the aspect ratio of the features becomes greater than one.
Accordingly, there has been a growing interest in developing CVD processes for deposition of refractory metal nitride thin films. For example, J. O. Olowolafe et al. reported in their article in J. Appl. Phys., 72, 4099 (1992) the results of an investigation of interdiffusion in Cu/CVD TiN thin-film structures. The results, however, showed that the low-pressure CVD TiN was stable up to 450.degree. C. for 30 minutes only, after which Cu started to diffuse through the TiN layer that served as the diffusion barrier and penetrate into the silicon substrate.
There was another attempt by R. Fix et at. in their article in Chem. Mater., 5, 614 (1993) to grow CVD TaN by using Ta(NMe.sub.2).sub.5 and ammonia chemistry, resulting in a tetragonal phase Ta.sub.3 N.sub.5 film. This tetragonal phase Ta.sub.3 N.sub.5 is known as a dielectric material with very high resistivity (greater than 10.sup.6 .mu..OMEGA.-cm). Such high resistivity hampers its usefulness as diffusion barrier for advanced metallization utilizing a metal such as Cu.